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nibble.go
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nibble.go
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// Copyright 2015 Matthew Collins
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package nibble
// Array is an array of 4 bit values.
type Array []byte
// New creates a new nibble array that can store at least
// the requested number of values.
func New(size int) []byte {
return make(Array, (size+1)>>1)
}
// Get returns the value at the index.
func (a Array) Get(idx int) byte {
val := a[idx>>1]
if idx&1 == 0 {
return val & 0xF
}
return val >> 4
}
// Set sets the value a the index.
func (a Array) Set(idx int, val byte) {
i := idx >> 1
o := a[i]
if idx&1 == 0 {
a[i] = (o & 0xF0) | (val & 0xF)
} else {
a[i] = (o & 0x0F) | ((val & 0xF) << 4)
}
}